Title Page
Contents
ABSTRACT 12
Ⅰ. INTRODUCTION 14
1. General introduction 14
1.1. Self-healing properties of polymers 14
1.2. Liquid-crystalline polymer 17
2. Research objectives 19
Ⅱ. EXPERIMENTAL 22
1. Materials 22
2. Experimental methods 22
2.1. Synthesis of mesogenic diol 22
2.2. Synthesis of self-healing liquid-crystalline TPUs 25
3. Characterization 28
3.1. Fourier-transform infrared spectroscopy (FT-IR) 28
3.2. ¹H nuclear magenetic resonance spectroscopy (¹H NMR) 28
3.3. Thermogravimetric analysis (TGA) 28
3.4. Dynamic Mechanical Analysis (DMA) 28
3.5. Gel permeation chromatography (GPC) 29
3.6. Differential scanning calorimetry (DSC) 29
3.7. Polarizing optical microscope (POM) 29
3.8. Self-healing properties of TPUs 29
Ⅲ. RESULTS AND DISCUSSION 31
1. Synthesis of mesogenic diol 31
1.1. Synthesis of hydroquinone-based mesogenic diol 31
1.2. Synthesis of isosorbide-based mesogenic diol 34
2. Synthesis of self-healing liquid-crystalline TPUs 36
2.1. FT-IR spectroscopy 36
2.2. ¹H NMR spectroscopy 38
2.3. Thermogravimetric analysis 40
2.4. Molecular weight 41
2.5. Dynamic mechanical analysis 42
2.6. Mechanical properties 45
3. Liquid crystal phase 47
3.1. Liquid crystal phase 47
3.2. Liquid crystal images via POM 50
4. Self-healing properties 52
4.1. Self-healing properties assessment through cutting 52
4.2. Tensile performance 54
4.3. Self-healing properties assessment through scratches 60
Ⅳ. CONCLUSION 62
Ⅴ. REFERENCES 63
ABSTRACT IN KOREAN 67
Table 1. Feeding ratio of monomers in self-healing liquid-crystalline TPUs. 27
Table 2. GPC results of self-healing liquid-crystalline TPUs. 41
Table 3. Dynamic mechanical analysis of self-healing liquid-crystalline TPUs. 43
Table 4. Mechanical properties of self-healing liquid-crystalline TPUs. 46
Table 5. Crystalline melting temperature (Tm) and isotropic temperature (Ti) of self-healing liquid-crystalline TPUs.[이미지참조] 48
Table 6. Young's modulus of self-healing liquid-crystalline TPUs subjected to self-healing properties assessment at various temperatures. 58
Figure 1. Self-healing process. 16
Figure 2. Types of self-healing mechanism. 16
Figure 3. (a) Liquid crystal phase and (b) liquid-crystalline polymer structure. 18
Figure 4. Design of self-healing liquid-crystalline thermoplastic polyurethanes with mesogenic diols and disulfide. 21
Figure 5. FT-IR spectrum of hydroquinone-based mesogenic diol. 33
Figure 6. ¹H NMR spectrum of hydroquinone-based mesogenic diol. 33
Figure 7. FT-IR spectrum of isosorbide-based mesogenic diol. 35
Figure 8. ¹H NMR spectrum of isosorbide-based mesogenic diol. 35
Figure 9. FT-IR spectra of self-healing liquid-crystalline TPUs. (a) SH-LCPU-H5D5 (b) SH-LCPU-H2D8 (c) SH-LCPU-I5D5 (d) SH-LCPU-I3D7 (e) SH-LCPU-D10. 37
Figure 10. ¹H NMR spectra of self-healing liquid-crystalline TPUs. (a) SH-LCPU-H5D5 (b) SH-LCPU-H2D8 (c) SH-LCPU-I5D5 (d) SH-LCPU-I3D7 (e) SH-LCPU-D10. 39
Figure 11. TGA curves of self-healing liquid-crystalline TPUs. 40
Figure 12. GPC diagrams of self-healing liquid-crystalline TPUs. 41
Figure 13. DMA curves of self-healing liquid-crystalline TPUs. 44
Figure 14. Stress-strain curves of untreated TPU samples. 45
Figure 15. DSC curves of self-healing liquid-crystalline TPUs and confirmation of crystalline melting temperature (Tm) and isotropic temperature (Ti).[이미지참조] 49
Figure 16. POM images of self-healing liquid-crystalline TPUs at varying temperatures. 51
Figure 17. Preparation of cutting self-healing assessment sample and assessment process. 53
Figure 18. Weight lifting demonstration (200g) of cutting self-healing assessment samples. The samples were healed at 120℃ for 10h. 53
Figure 19. UTM measurement process of healed sample. 56
Figure 20. Stress-strain curves of healed self-healing liquid-crystalline TPUs. 57
Figure 21. Tensile strength and healing efficiency of healed TPU samples. 59
Figure 22. OM images of scratch self-healing assessment. 61
Scheme 1. Synthetic routes of mesogenic diols. 24
Scheme 2. Synthetic routes of self-healing liquid-crystalline TPUs. 26